Yes. You can run several WinDriver-based applications simultaneously on the same machine. (With regard to accessing the same hardware from several applications, please refer to Technical Document #98.)

Until version 11.5.0, code developed with an earlier version of WinDriver could run with the drivers from a newer version as well (provided the code wasn’t recompiled with newer header files using the old license). At most, you may have needed to update the INF files for PCI/USB devices when upgrading the driver on a Plug-and-Play OS.
Staring from version 11.5.0, code developed with an earlier version needs to be recompiled with a new license that matches the version of the newer WinDriver driver with which you want to use the code. See additional information in Technical Document #84,

Note that code developed with a newer version of WinDriver was never guaranteed to work with an older driver file. You should, therefore, take care, when distributing your driver, that the installation process does not overwrite a newer version of the WinDriver module —windrvr.sys/.o/.ko/.dll (orwindrvr6.sys/.o/.ko/.dll/.vxd / windrvr.sys/.vxd/.o, in earlier versions of WinDriver), or a renamed version of the driver — with an older version of the driver file. This is also true for the WinDriver USB Linux GPL driver — windrvr_usb.o/.ko (previouslywindrvr6_usb.o/.ko; from WinDriver v10.0.0 and above).

In version 6.0 of WinDriver we renamed the WinDriver kernel module from windrvr to windrvr6. In version 11.9.0 we renamed the default kernel module to windrvr (e.g.,windrvr1200). WinDriver kernel modules with different names can be used simultaneously on the same machine.