A LINEMAN NOTED PARKING BRAKE (P/B) WAS SET BFR FLT. PLTS BGN TKOF ON 5147' RWY WITH 10 KT X-WND. A WITNESS SAID ACFT ROTATED FOR TKOF ABT 4500' DWN RWY & LIFTED OFF ABT 50' LTR. RPRTDLY, IT RMND LOW & SLOW (20-60 FT AGL) AFTER LIFT-OFF, THEN BANKED (ROCKED) LEFT & RIGHT IN NOSE HI ATTITUDE, SETTLED, HIT TREES & CRASHED ABT 200' BYD RWY. ONE PERSON SAID ACFT WENT OUT OF CTL BFR IMPACT; ANOTHER SAID IT WAS 'IN OR ON THE EDGE OF STALLED FLIGHT.' EXAM SHOWED ROTATIONAL DMG OCCURRED IN BOTH ENGS DRG IMPACT. THE BRAKING SYS HAD EVIDENCE THAT P/B CTL VLV WAS PARTIALLY ON; BRAKE TORQUE TUBE CONTAINED HEAT BLUEING. ON THIS EARLY MODEL (LEARJET 23/SN: 23-45A), P/B HAD TO BE RLSD BY DEPRESSING BRAKE PEDALS 1ST; PLT HANDBOOK DID NOT ADDRESS THIS. ON LTR MODELS (SN: 23-050 & UP), P/B NEEDED ONLY TO BE MOVED 'OFF.' INV SHOWED LEFT SEAT PLT HAD TRNG IN LATER MODELS (LEARJET 24/25); BUT ONLY A BIENNIAL FLT REVIEW WAS NOTED IN THE MODEL 23. COMPANY DISPATCHER SAID NO TRNG WOULD HAVE BEEN PERFORMED ON ACDNT FLT (WITH PSGR ABOARD). ACFT WAS ABT 430 LBS OVR MAX WT LMT.