Original from CCC, let's try to compile with sdcc for it.
https://events.ccc.de/camp/2007/Fahrplan/attachments/1337‑Sputnik%20Slides 
The OpenBeacon Tag consists of
nRF24L01 2.4GHz transceiver (1/2MBps)
 PIC16F684 PIC14 microcontroller

Contents: [Dobrica Pavlinušić's random unstructured stuff]
• Dobrica Pavlinušić's random unstructured stuff (Schematics) 
• Dobrica Pavlinušić's random unstructured stuff (pinout) 
• Dobrica Pavlinušić's random unstructured stuff (PicKit 2) 
• Dobrica Pavlinušić's random unstructured stuff (Source) 
• Dobrica Pavlinušić's random unstructured stuff (archival links) 

Schematics
OpenBeacon.pdf 

pinout
(same as pickit)
1 VPP/RA3 (Square pin)
 2 VDD
 3 GND
 4 ICSPDAT/RA0
 5 ICSPCLK/RA1 (also connected to touch sensor)
 6 PGM (seems to be unconnected)
PicKit  2
pi@rpi2 ~ $ git clone https://github.com/psmay/pk2cmd
pi@rpi2 ~ $ cd pk2cmd/pk2cmd
pi@rpi2 ~/pk2cmd/pk2cmd $ make linux

pi@rpi2 ~/pk2cmd/pk2cmd $ ./pk2cmd -P
Auto-Detect: Found part PIC16F684.

# power on target of pickit 2 which is sputlink tag
pi@rpi2 ~/pk2cmd/pk2cmd $ ./pk2cmd -PPIC16F684 -T

Source
dpavlin@klin:/rest/cvs$ git clone https://github.com/meriac/openbeacon

archival links
• https://web.archive.org/web/20111119165129/http://www.openbeacon.org/dl/23C3/OpenBeacon.pdf