I emailed Thomas Bradley when I was exploring options and he responded within an hour. Also, that repository was active (TB was responding to bug reports and there had been commits on the day that I looked) and had more followers and forks. Since I'm a mediocre hacker, I generally optimize for paths where I can get the most support if I think I might need it.
Thomas's is also very well documented with specific code examples and demos for the basic use cases.
I considered a lot of different options, including signature as a service (https://www.signature.io/ -- these guys have a beautiful implementation), integration with other companies (hellosign and signnow are my favorites, docusign/echosign), but TB's was just the best fit for my needs at the time.