Can I Use GPL In Closed Source?
@eMAD parts of it can, yes. For example if it has GPLed JavaScript, then the source code for that must be available.
The GPL licenses are the most common open source licenses and generally the most problematic for companies developing software. SaaS companies are more free to use GPL licensed-code because the obligations of the GPL are triggered upon software distribution and SaaS software by nature is not distributed.
Are SaaS companies immune to open source risk? - Synopsys
Can I use GPL software on my website?
You are free to run a GPL-licensed program without having to accept the license. If the GPL'ed program is client-side JavaScript, then you are distributing the GPL'ed code and possibly derivative code to your visitors. You are only allowed to do this in accordance with the GPL.
website - Can I use a GPL component in my site without having to disclose ...
Can you use GPL code in proprietary software?
Under the GPL, either static or dynamic linking requires the main program to be distributed under the GPL, with the result that linking a GPL-licensed library is incompatible (in licensing terms) with a proprietary program.
Using GPL code in your software: the essentials - Clendons
Does the GPL license require the author to release the modified source code? GPL requires you to release the modified source code only if you release the modified program. If you've modified a program's source code for personal use, there's no need to release its source code.
GPL License - Top 10 Questions Answered - Mend