I went through the EMR list at http://en.wikipedia.org/wiki/List_of_open_source_healthcare_software and tried out the ones I could get my hands on. Here's a summary of what I found.
Legend:
? - unable to verify
N/A - feature not available
F - crashes or doesn't work
C - limited functionality, bad interface
B - decent functionality, bad interface
A - decent functionality, decent interface
| EMR | License | Platform | Scheduler | SOAP | Billing | Usability |
|---|---|---|---|---|---|---|
| ClearHealth | GPL | Web | ? | ? | ? | ? |
| FreeMedForms | BSD | Native | F | N/A | N/A | F |
| FreeMED | GPL | Web | C | N/A | N/A | C |
| GNUmed | GPL | Native | C | B | N/A | C |
| GNU Health | GPL | Native | C | C | C | ? |
| OpenEMR | GPL | Web | B | B | C | C |
| OpenMRS | Custom (GPL-like) | Web | N/A | N/A | N/A | B |
| Oscar | GPL | Web | B | B | C | C |
As far as I can tell, it's a toss up between OpenEMR and Oscar. We'll need to take a closer look at both their billing systems to figure out which one is closer to what we want.