The iwl3945 driver is Free Software(Licence GPLv2) however proprietary microcode is needed for it to work, otherwise it will just throw some error messages in dmesg when trying to use wpa_supplicant.

dmesg

[  273.314507] 0000:0c:00.0: Missing Free firmware (non-Free firmware loading is disabled)
[  273.314549] iwl3945 0000:0c:00.0: /*(DEBLOBBED)*/ firmware file req failed: -2
[  273.314552] 0000:0c:00.0: Missing Free firmware (non-Free firmware loading is disabled)
[  273.314578] iwl3945 0000:0c:00.0: /*(DEBLOBBED)*/ firmware file req failed: -2
[  273.314582] iwl3945 0000:0c:00.0: Could not read microcode: -2
[  390.095749] 8021q: 802.1Q VLAN Support v1.8
[  390.156641] 0000:0c:00.0: Missing Free firmware (non-Free firmware loading is disabled)
[  390.156670] iwl3945 0000:0c:00.0: /*(DEBLOBBED)*/ firmware file req failed: -2
[  390.156671] 0000:0c:00.0: Missing Free firmware (non-Free firmware loading is disabled)
[  390.156687] iwl3945 0000:0c:00.0: /*(DEBLOBBED)*/ firmware file req failed: -2
[  390.156688] iwl3945 0000:0c:00.0: Could not read microcode: -2
[  497.798939] 0000:0c:00.0: Missing Free firmware (non-Free firmware loading is disabled)
[  497.798980] iwl3945 0000:0c:00.0: /*(DEBLOBBED)*/ firmware file req failed: -2
[  497.798983] 0000:0c:00.0: Missing Free firmware (non-Free firmware loading is disabled)
[  497.799010] iwl3945 0000:0c:00.0: /*(DEBLOBBED)*/ firmware file req failed: -2
[  497.799013] iwl3945 0000:0c:00.0: Could not read microcode: -2

lspci -vmmnn

Slot:	0c:00.0
Class:	Network controller [0280]
Vendor:	Intel Corporation [8086]
Device:	PRO/Wireless 3945ABG [Golan] Network Connection [4222]
SVendor:	Intel Corporation [8086]
SDevice:	Device [1021]
Rev:	02

lspci -nnk

0c:00.0 Network controller [0280]: Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection [8086:4222] (rev 02)
	Subsystem: Intel Corporation Device [8086:1021]
	Kernel driver in use: iwl3945
	Kernel modules: iwl3945

lspci -vvnnk

0c:00.0 Network controller [0280]: Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection [8086:4222] (rev 02)
	Subsystem: Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection [8086:1021]
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0, Cache Line Size: 64 bytes
	Interrupt: pin A routed to IRQ 25
	Region 0: Memory at fe8ff000 (32-bit, non-prefetchable) [size=4K]
	Capabilities: [c8] Power Management version 2
		Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
		Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
		Address: 00000000fee01004  Data: 4027
	Capabilities: [e0] Express (v1) Legacy Endpoint, MSI 00
		DevCap:	MaxPayload 128 bytes, PhantFunc 0, Latency L0s <512ns, L1 unlimited
			ExtTag- AttnBtn- AttnInd- PwrInd- RBE- FLReset-
		DevCtl:	CorrErr- NonFatalErr- FatalErr- UnsupReq-
			RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+
			MaxPayload 128 bytes, MaxReadReq 128 bytes
		DevSta:	CorrErr- NonFatalErr- FatalErr- UnsupReq- AuxPwr+ TransPend-
		LnkCap:	Port #0, Speed 2.5GT/s, Width x1, ASPM L0s L1, Exit Latency L0s <128ns, L1 <64us
			ClockPM+ Surprise- LLActRep- BwNot- ASPMOptComp-
		LnkCtl:	ASPM Disabled; RCB 64 bytes Disabled- CommClk+
			ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
		LnkSta:	Speed 2.5GT/s (ok), Width x1 (ok)
			TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt-
	Capabilities: [100 v1] Advanced Error Reporting
		UESta:	DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
		UEMsk:	DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
		UESvrt:	DLP+ SDES- TLP- FCP+ CmpltTO- CmpltAbrt- UnxCmplt- RxOF+ MalfTLP+ ECRC- UnsupReq- ACSViol-
		CESta:	RxErr- BadTLP- BadDLLP- Rollover- Timeout- AdvNonFatalErr-
		CEMsk:	RxErr- BadTLP- BadDLLP- Rollover- Timeout- AdvNonFatalErr-
		AERCap:	First Error Pointer: 00, ECRCGenCap- ECRCGenEn- ECRCChkCap- ECRCChkEn-
			MultHdrRecCap- MultHdrRecEn- TLPPfxPres- HdrLogCap-
		HeaderLog: 00000000 00000000 00000000 00000000
	Capabilities: [140 v1] Device Serial Number 00-1c-bf-ff-ff-65-c2-b7
	Kernel driver in use: iwl3945
	Kernel modules: iwl3945