Then, if I download it, and I made some modifications at the source code, the AGPL (under certain conditions) will bind me to publish the source code.
Note that the "(under certain conditions)" is offering remote use of the software you've modified, and you must only offer it to those who are using your software.
I see two major errors on the AGPL. One, that binds the occasional developer to make their modified work public.
Only when and to those using your software remotely. Likewise, with the GPL, an "occasional developer" must also make her/his modified source available to those they send their object code to.
And two, that forbids the possibility of selling it, because you are forced to share it for free.
You can sell access to the software, and give the source to those who've already paid for this service.
The only time the AGPLv3 section 13 requires you to make your modifications "public" is when your modified version is "public".
For example, say that I have a company, and we downloaded the meneame.net
source code and we've improved it. Then I'll sell to "Joe" for 200 Euro. Joe
now has a CD-ROM with the modified source and wants to try it at home with his
IRC friends. But Joe doesn't have a Internet connection, It only has a GPRS
modem. His internet provider will bill for each Megabyte.
Should Joe upload that source code? and, what If Joe doesn't want to make that code public?
This is akin to saying, "Joe only has a GPRS modem, and gives someone a modified binary, the source code is a lot bigger, thus it's a financial burden to Joe to comply with the GPL".
If license compliance is a financial problem for Joe, he better consider that before he buys modified source from someone who isn't willing to include hosting the source code online as part o the sale.