Not directly compatible. Was made OEM by X10 as it has an X10 Grantee FCC ID, but it uses a different RF Frequency. X10s are 310Mhz; Freewire 418Mhz. You will need a Freewire Messenger Hub to receive the FWMD Motion sensor. Once you get to the powerline signals. A Freewire Messenger Hub can control an X10 module and an X10 controller can control a Freewire module. I have used them in both directions. I do like the Freewire Messenger Hubs need of registering [like an X10 Security Console] the remotes. So you can have two hubs and remotes only control the hub it is registered to. Also the Messenger Hub has the house code dial and the Master Remote can do all 16 unit codes to the hub it is registered to.
One more thing. In the FCC database all the Freewire RF devices schematics and photos where released for public viewing. Some of the X10 stuff is also there like the cm15a USB Interface.
I'm using the "weather proof" modules on some exterior holiday lighting using regular X10 commands. The trick is to plug in their transceiver and"teach" the modules a code using a standard x10 signal instead of the remote that is furnished with the kit. After that you can remove the B&D transceiver and control the modules with any x10 controller. And the modules do stay coded if/when you unplug them.
We sell the Freewire line, and the products are 95% X10 compatible, the 5% being the previously mentioned RF frequency differences. I have personally installed the motion detectors (FWMD), they do require the messenger hub (FWMH) but work perfectly with X10 from that point. I have customers using them to trip home automation software as well as standard X10 modules with no problem. I also personally have the outdoor lamp modules (FWLROD) running Christmas lights with no difficulties.
We do have a sale currently for the 5 piece kit, I dont know the boards regulations on posting links and/or sales which would be considering "advertising" so if the admins allow I would be more then happy to post it.
Minor threadjacking, I would also like to offer a discount to all forum members making purchases by using a coupon code, however I still am wary without admin permission to do so.