Its just means that if you change the code of SŌZU you'll have to have your fork public on GitHub.. Not a big deal.
Google has a policy against using APGL internally, nor in your company equipment[0].
The primary risk presented by AGPL is that any product or service that depends on AGPL-licensed code, or includes anything copied or derived from AGPL-licensed code, may be subject to the virality of the AGPL license. This viral effect requires that the complete corresponding source code of the product or service be released to the world under the AGPL license.
As for the spreading to other programs part, yes that's the entire point, if you use free code, anything built on it should be free too, to continue giving to the Free/open Eco system.