In a nutshell, yes, the ownership of your MemberGate license is probably transferable (not guaranteed), but there are a lot of details that need to be answered before you would want to make a final decision. It would be best for you to email us at support so a clearer picture can be provided of what is involved such as costs and other factors.
The license agreement indicates you own all of the content on your site. Most likely, there won't be a problem if the content of your site is going to continue as is. MemberGate does not license to sites with specific content (adult, hate sites, etc).
The costs that could be involved include redoing paperwork, reconfiguring the site, graphic design changes as needed and software upgrades as needed.
Finally, since we will be giving support among other things, we would like to familiarize ourselves with the new owner.