The do not say what is different about individual Dash 3gs that affect the level of compatibility, but mine came with WM 6.5 and WmWifiRouter was the first program I installed on it, the other software being just the standard stuff that came with the phone.Compatibility with the Dash 3G has been varied according to user reports. While tapping the power button should shut off the display and allow WMWifiRouter to work in low-power mode, some non-compatible / semi-compatible devices do not allow WMWifiRouter to work in low-power mode. Your best bet is to give it a try."
Based on personal experience, WMWiFi Router Versions 1.30 and 1.35 worked well on T-Mo's Dash 3g. (Including Display Off)
The Display, or backlight did not turn off using other 1.x versions, so I am aware of this issue. (I have not used the 2.x version)
Originally I used, downloaded WMWiFi Router 1.30 trial from their website on an Ubiquio 503g (worked well)
I presently am using version 1.6x on a TP2 and HD2. My original key worked in this upgrade. I do not know if the same key would be compatible in the 2.x series.
I do not have the Dash 3g or the earlier version of WMWiFi Router any longer, or I would send it to you. Maybe you could request the older trial version from WMWiFi Router's support