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(Ironically, web apps are an area where you can generally get away with not knowing anything about open source licenses, since you're not redistributing the pro

(Ironically, web apps are an area where you can generally get away with not knowing anything about open source licenses, since you're not redistributing the programs you make.) Except if you happen to use something under an Affero GPL license, in which case you really should know about it. But yes, those project are rare.

mikeash 12y ago
I hadn't heard of that one. Is it actually enforceable? I was under the impression that the GPL didn't require opening server code, not because it was missing something, but because server code doesn't get distributed and thus doesn't fall under copyright limitations in the first place.
- TuringTest 12y ago
  The Affero GPL is a modificated version of the common GPL that explicitly handles the case of software used as a service through internet. It's fairly uncommon, but those projects licensed with this version have specific function built in that allows any user to get a copy of the source code (and you couldn't remove it without breaching the license); and some known names use it (MediaGoblin, MongoDB, Diaspora, Ghostscript, Launchpad, POV-Ray are some examples).
- Flimm 12y ago
  You find a library on the Internet somewhere. What entitles you to copy it onto your machines? Copyright does not allow to do this, so you are reliant on a license to give you permission to do this. GPL gives you permission to do this, as long as when you distribute any modifications of it, you also pass along the source code. AGPL gives you permission to do this, as long as you give the source code to all of your users should they request it. If you can't meet the conditions, than you don't get the rights acquired by the license, and you fall back to default copyright, which says it's illegal to have copied the library to your own machines in the first place.
- belorn 12y ago
  AGPL enforceability (under copyright) rests on the concept of modification rights. The basic idea is that one must get copyright permission in order to modify a protected work, which then AGPL adds conditions for. This has been semi-tested in the past. In a court case regarding sold paintings, the court sided with the painter when the buyer wanted to chop the art into pieces and rearrange them. The court decided that the act of modifying the art created an derivative work which the painter had not given the buyer permission for.

mikeash 12y ago

I hadn't heard of that one. Is it actually enforceable? I was under the impression that the GPL didn't require opening server code, not because it was missing something, but because server code doesn't get distributed and thus doesn't fall under copyright limitations in the first place.

TuringTest 12y ago
The Affero GPL is a modificated version of the common GPL that explicitly handles the case of software used as a service through internet. It's fairly uncommon, but those projects licensed with this version have specific function built in that allows any user to get a copy of the source code (and you couldn't remove it without breaching the license); and some known names use it (MediaGoblin, MongoDB, Diaspora, Ghostscript, Launchpad, POV-Ray are some examples).
Flimm 12y ago
You find a library on the Internet somewhere. What entitles you to copy it onto your machines? Copyright does not allow to do this, so you are reliant on a license to give you permission to do this. GPL gives you permission to do this, as long as when you distribute any modifications of it, you also pass along the source code. AGPL gives you permission to do this, as long as you give the source code to all of your users should they request it. If you can't meet the conditions, than you don't get the rights acquired by the license, and you fall back to default copyright, which says it's illegal to have copied the library to your own machines in the first place.
belorn 12y ago
AGPL enforceability (under copyright) rests on the concept of modification rights. The basic idea is that one must get copyright permission in order to modify a protected work, which then AGPL adds conditions for. This has been semi-tested in the past. In a court case regarding sold paintings, the court sided with the painter when the buyer wanted to chop the art into pieces and rearrange them. The court decided that the act of modifying the art created an derivative work which the painter had not given the buyer permission for.