Most proprietary software with EULAs does not contain a copyleft provision that forces itself upon other software. I find copyleft creepy and power-hungry, so my choice of word reflects how I perceive it.
an agpl lisc only requires that you provide the code you altered in order to integrate. prohibiting it from running on their servers simply closes the door on people coming to them for code they don't even own!
The use of the word “infection” is usually deliberate and an attempt to taint users view of GNU’s software licenses.