At crunchgear.com the latest news is that Google seems to have decided to reintroduce the tethering apps to the Android Market. However: this change of mind is not without restrictions. According to Crunchgear.com, the terms of use prohibit offering the tethering apps on T-Mobile US (which probably also applies to T-Mobile Germany). So apparently only G1 users without T-Mobile as network operator can enjoy the tethering apps.
Crunchgear also suspects that T-Mobile may be developing an application that will turn the G1 into a mini-WLAN hotspot with 3G UMTS Internet. But: if such a feature comes from the network operator it is quite possible that a monthly fee will be charged.
Let's hope that after Google, T-Mobile will change its mind and Android will become an open platform.