I was looking at doing what you were suggesting with a Dry DSL line and whole house wiring. My house phone was wired in with DSL using what looks like Cat 5E cable from the outside and through out the house. The only line being used was the blue (blue and blue/white) pair. I had the Orange, Green and Brown pairs run everywhere but not used (eight wires or four pair total).

What I was going to do is leave the blue pair hooked up to the phone company for DSL as it is now and then use the Orange and Green pairs (Orange with Orange/white as well as Green with Green/white) to carry the other two lines. Line one would be orange and Line two would be green. I think that if budmaster had the same type of set-up, they could do this. In all of the phone jack boxes in the house, make sure all of the same color wires are connected. Blue with Blue, Blue/White with Blue/White, Orange with orange, and so on. In the box that I would be using for the DSL modem connnection and the VOIP box I would place three jacks. I like using the Leviton Modular ones that I can get at Home Depot (you can snap up to six into a single wall plate that has the pre-cut holes). For the DSL jack, you could hook the blue pair up to the blue punch down terminals (the main line plugged into this jack is now associated with the blue pair). For line one off of the VOIP box, I would install a jack with the orange pair off the cables hooked to the blue push down terminals on the jack (the main line plugged into this jack is now associated with the orange pair). For line 2 off the VOIP box, install the Green pair again to the Blue punch down terminals (and the main line plugged into this jack will be associated with the Green pair). Anywhere in your house now, you should have DSL on the blue pair, Line one from VOIP on the orange pair, and Line 2 from VOIP on the green pair. You could hook up new jacks around the house (with the Leviton jacks) you wouldn't match colors for the phone jacks though. I think for phone jacks (not DSL jacks), you would hook the orange pair up to the blue terminals, and the green pair to the orange terminals. Sounds confusing, but you are leaving DSL on line 1 in the cables, carrying your line 1 voip on the second line in the cables, and carrying line 2 voip on the third line in the cables. Make sure all lines are disconnected from the phone company.

I got lucky--just switched to cable modem before getting VOIPo. I will disconnect from phone company all together (it will be a happy day). On all the phone jack boxes except for one, I will just match the colors on the terminals on the back of the pone jack with the colors of the wires. On the jacks by my VOIPo box, I will hook the blue pair to the blue terminals to plug line 1 from the box into. I will hook the orange pair to the blue terminals on the jack that I will plug the second VOIP line into.

I just thought of a better idea for the Dry DSL case that would be similar to my cable modem case. switch DSL over to the fourth line (brown) at the phone company box (unhook the blue pair and hook up the brown pair to the phone service for the DSL). Then in all of the boxes in the house except the one by the VOIP / DSL modem boxes, you can just connect similar color wires and leave the termination to the jacks matching the standard colors. At the VOIP / DSL modem box, hook the brown pair to the blue posts on the jack to be connected to the DSL modem. Hook the blue pair to the blue posts on the jack hooked to line 1 from the VOIP box. Hook the orange pair to the blue posts on the jack that will connect to the line 2 on the VOIP. If you do this, Line 1 VOIP phone is in Line 1 in your wiring (blue pair), Line 2 VOIP phone is on Line 2 in your wiring (orange pair), and the DSL is on Line 4 in your wiring (brown pair). I guess you could switch green for brown in these examples.

I hope this helps. I don't know if it follows all conventions, but it should work. Where all of the colors on the wires match the colors on the jacks in every place but the phone company box and the box with the three jacks for the DSL Modem / VOIP box, the last suggestion is probably the easiest to still know what you have in two years.