Comment by cbsks

GPL v3.0 has a SaaS loophole. The GPL's trigger is conveyance (transferring a copy), not network access. Merely running modified GPL v3.0 code on a server and serving users over HTTP is not "conveying" under the letter of GPL v3.0, so it does not by itself obligate you to release source. This loophole was fixed in AGPL v3.