The code being distributed under a source available license does not give you a right to take it, modify it, or redistribute it.
I would add in “automatically” there. Source-available licenses could give you the right to modify it and redistribute it, or it may not. For example, the Unreal Engine is proprietary and covered by a source-available model, and you can redistribute it to other license holders (must accept certain terms and conditions), and even then w/ restrictions. So you can take it, modify it, and redistribute it, but there are a handful of very important asterists there.
Basically, if you don’t recognize the license as one of the major ones (Apache, BSD, MIT, (L|A)GPL, etc), then treat it as source-available w/ no rights other than reading it until you actually read and understand the license.
even if it is FOSS, it might still have a restrictive license
Likewise, this is definitionally untrue. The whole purpose of FOSS is to give you the four freedoms.
That depends on your definition of “restriction.”
If you use a copyleft license, you could be restricted from using proprietary plugins, since you’d have to release the source of those plugins if a user accesses it in a covered way, and you don’t have the right to do that. That sounds like a restriction to me, and it doesn’t apply to more permissive licenses like BSD or MIT.
The intent of copyleft is to ensure freedoms for the recipients of derivatives of your works. In software that means the users of forks. Copyleft restricts you to the same license (or a compatible one) to prevent you adding more restrictions. ““More permissive”” software licenses can be redistributed with the same license but often it’s a more restrictive license (e.g. MIT -> proprietary).
You can’t remove the license, say MIT, or add any restrictions to the code. You can combine it with other works and distribute the combined work under different terms, provided you still abide by the terms of the license (e.g. source distributions need to retain the license, binary distributions don’t).
Copyleft forces modified distributions to have the same terms as the copylefted software. If you have some MIT code and some GPL code and you combine it, the combined work is GPL. Likewise if you combine proprietary code and GPL, the combined work is GPL, and that’d regardless of how it’s distributed.
Permissive licenses protect the source as it was when it was combined into the other work. Copyleft licenses enforce distributed changes to the source are made available under the same license. Which one you want depends on what “freedoms” you want. Do you want the freedom to use the source however you want, including with proprietary code? Then you want a permissive license. Do you want to ensure that any changes to the code are always available? Then you want copyleft code.
I would add in “automatically” there. Source-available licenses could give you the right to modify it and redistribute it, or it may not. For example, the Unreal Engine is proprietary and covered by a source-available model, and you can redistribute it to other license holders (must accept certain terms and conditions), and even then w/ restrictions. So you can take it, modify it, and redistribute it, but there are a handful of very important asterists there.
Basically, if you don’t recognize the license as one of the major ones (Apache, BSD, MIT, (L|A)GPL, etc), then treat it as source-available w/ no rights other than reading it until you actually read and understand the license.
That depends on your definition of “restriction.”
If you use a copyleft license, you could be restricted from using proprietary plugins, since you’d have to release the source of those plugins if a user accesses it in a covered way, and you don’t have the right to do that. That sounds like a restriction to me, and it doesn’t apply to more permissive licenses like BSD or MIT.
The intent of copyleft is to ensure freedoms for the recipients of derivatives of your works. In software that means the users of forks. Copyleft restricts you to the same license (or a compatible one) to prevent you adding more restrictions. ““More permissive”” software licenses can be redistributed with the same license but often it’s a more restrictive license (e.g. MIT -> proprietary).
You can’t remove the license, say MIT, or add any restrictions to the code. You can combine it with other works and distribute the combined work under different terms, provided you still abide by the terms of the license (e.g. source distributions need to retain the license, binary distributions don’t).
Copyleft forces modified distributions to have the same terms as the copylefted software. If you have some MIT code and some GPL code and you combine it, the combined work is GPL. Likewise if you combine proprietary code and GPL, the combined work is GPL, and that’d regardless of how it’s distributed.
Permissive licenses protect the source as it was when it was combined into the other work. Copyleft licenses enforce distributed changes to the source are made available under the same license. Which one you want depends on what “freedoms” you want. Do you want the freedom to use the source however you want, including with proprietary code? Then you want a permissive license. Do you want to ensure that any changes to the code are always available? Then you want copyleft code.