[mgkimsal]

HeyLaughingBoy nailed it, but there's another couple of points that got missed in the replies/discussion.

1. It's not "free work", it's just ... stuff you do. Maybe you release it out and other people benefit from it, maybe you just do it to demonstrate skills.

2. Per #1, you get to demonstrate whatever you want to learn. Do you want to learn how to use Twilio APIs? You could wait for a client engagement that might need Twilio, or you could try to force Twilio in to a client project where it's not needed, or you could... just play with Twilio, produce something demonstrable, and use that to show what you know about using Twilio. It's great when you can show your skills having real value to real past client projects, but absent that demonstration and experience, you'll be experimenting on your new clients to a degree. Learning on your own dime (and time) can also inspire a degree of confidence that you actually know XYZ before you're engaged to do XYZ.