Tweetduck - Open source, seems active, supports multiple accounts, and lists a portable version (will try to test soon)
https://github.com/chylex/TweetDuck/releases
http://www.softpedia.com/get/Internet/C ... Duck.shtml
Other possibilities
- Tweeten - lots of features, cross-platform but 64-bit only (difficult to test on my current setup, not fundamentally very portable):
http://tweetenapp.com/
http://www.softpedia.com/get/Internet/C ... eten.shtml - Tweelectron - Intended as a replacement for the "TweetDeck for Desktop" app, this is electron-based (unlikely to be portable) but works with Tor so you can have some privacy:
https://github.com/Plastikmensch/Tweelectron
http://www.softpedia.com/get/Internet/C ... tron.shtml - Microblog - purple: Long-dead project for a Pidgin plugin:
https://code.google.com/archive/p/microblog-purple/ - Official client: "Twitter for Windows 10/8" but I have Windows 7
http://www.softpedia.com/get/Internet/C ... ws-8.shtml