Echo audio drivers
For those who are interested in, here's what the Echo Digital Audio Corporation' Software Developer Page claims:
Interested in writing your own driver for Echo’s hardware? Then you need the generic driver code. This is the cross-platform C++ library used for our Windows and Mac PCI and Cardbus drivers.
Source code is provided under the terms of the GNU Lesser General Public License.

Comments
Re: Echo audio drivers
Looks like Haiku already has Echo drivers:
http://svn.berlios.de/viewcvs/haiku/haiku/trunk/src/add-ons/kernel/drive...