Tmobile offers direct offers for special groups, one is for HTC developers.  There is no verfication from Tmobile if you are a developer or not, just use the code.

T-Mobile G1 for $139.99
Free BT Headset (jabra / motorola)
Free Companion Flight (purchase one and get one free)                                     Waived Activation Fee ($35)
Free Shipping (2-day)

To do it
1. Call 1-866-464-8662 (select option 3)
2. Say you have a  promo code: 8291TMOFAV
for the HTC Developer Promo