PhonerLite (and partially Phoner) supports the following encryption methods:

TLS:

• Encryption of a SIP connection
• No end-to-end encryption is used. Using any SIP server (provider or PBX) with TLS support, that SIP server can decrypt these SIP messages - it has to do so, else it can't handle/switch that call
• Usage of certificates

SRTP:

• Encryption of audio data (speech)
• Normally the key exchange is done within the SIP connection. Therefore it only makes sense to use SRTP in conjunction TLS, else the keys can be "sniffed"
• A SIP-to-SIP connection using a SIP server doesn't guarantee an end-to-end encryption, because the server knows the keys.

ZRTP:

• ZRTP is a protocol using the same communication path as the audio data. The key exchanges is done directly between the two endpoints.
• An end-to-end encryption is guaranteed, but only between SIP-to-SIP connections
• ZRTP is a special way to exchange secret keys only. After key exchange a "normal" SRTP encryption is done with that keys.

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If you are using a VoIP provider that routes your call to the public telephony network, there is no encryption on that public telephony line.

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Where do you see a problem with a license?

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ZRTP is only the way the keys are exchanged. After key exchange SRTP is used with that keys. So ZRTP is only used with SRTP together.
Put your mouse cursor above the SRTP icon - a tooltip will appear. If that tooltip only tells you "SRTP", the key was exchanged within the SIP messages. If there is "ZRTP: abcde", ZRTP was used for key exchange, "abcde" will be the SAS (Short Authentication String) for that session. Both sides should see the same SAS and can control by telling that string to each other, if there real end-to-end encryption and no man-in-the-middle is "listening".

i mean explicitly show zrtp established, like some led or color. saas by moving mouse over is alright

I am using xlite. 
Zrtp is another way to exchange keys with SRTP. But I think it is very important one. So an explicit indication is very important so the user knows that it is doing zrtp. Currently its so difficult and unobvious to tell. Please try to understand that if user doesn't know or can't tell whether or not these secure methods are running or not, it reduces the value of the method to some extent also. In zfone if you see, it will show so explicitly and big way. Thank you!

If you have an encrypted call you should get a new icon near by the dial buttons. Only that icon shows you the tooltip if you are using SRTP with ZRTP based keys.
The only task of Zfone is to encrypt data for other softphones. So it shows that encryption status with big icons. For that application it is OK, but such big icons would not fit in PhonerLite.

You have enabled ZRTP on both PhonerLite instances? Is there any special device (IP-PBX) in the middle of both?
I have no problems with two PhonerLite in version 1.84! Only a wireshark can help to identify any problem.
Perhaps you should test with ZFone before to test your infrastructure.

I have no problems at all with ZRTP here in any test environment.
You should check of Zfone works properly or if any security application or firewall skips that ZRTP messages.
If you don't want to use Zfone you can use SIP Communicator too.

what is your test environment ? what server are you using ?