Pay OR liCENSE for jqGrid?

No. This package is free, distributed under GPL and MIT, so you don't need to pay. Just follow the GPL rules and everybody will be happy. I really was needing some way to contribute to the open source community, and I hope this is just the beginning.
If you really love jqGrid and wish to make a donation, you can contact  Mr.Tony at [email protected]. HE is the Inventer og JQ Grid