TIA is not free software, but there is a free two-week trial period and it is very cheap to register.
"So what do I run on my machine at home?"
Exactly the same software you would use for real SLIP; as far as your PC is concerned, it is a SLIP connection. If you're unfamiliar with SLIP please check out a newsgroup relevant to your particular type of PC (Windows, Mac, etc). (This isn't restricted to common systems; because all the emulation happens on your Unix shell account, your client machine can run anything that supports SLIP.)
"Details, please! I'm confused."
Check out the TIA home page (URL is http://marketplace.com/tia/tiahome.html ), or send email to info@marketplace.com and request details about TIA.
If you have a Macintosh, check out the Macintosh TIA Users' FAQ (URL is: ftp://ftp.netcom.com/pub/bi/billa/tia/faq.html ) for additional help.