The 21-year-old scored twice for the non-league team in their FA Cup first-round defeat by Carlisle in November.
Morais has previously played in the Football League for Wycombe.
"He has scored some great goals already this season for St Albans, and we are pleased to have secured his signature," said Posh boss Grant McCann.
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A test transmission has already begun on Freeview channel 23 in south east Wales.
The broadcaster will be based at Elgin House in St Mary Street in the city centre and will have around 20 staff.
The Made TV group holds licences for local TV in Cardiff, Bristol, Leeds, Middlesbrough and Newcastle.
The other two local TV stations in Wales, Bay TV Swansea and Bay TV Clwyd in Mold, are both due to launch in 2015.
Made in Cardiff will shortly appear on the Sky satellite TV service in the area on channel 134, and Virgin Media channel 159.

Alan Bennett, of Lingholme, Redcar, was at Teesside Magistrates' Court for the short hearing during which he confirmed his name and address.
He is accused of murdering Lynne Freeman, 46, and 30-year-old Jodie Betteridge, on Wednesday evening.
He was remanded in custody and will appear at Teesside Crown Court on 29 March.
Police were called to Mapleton Crescent, where Mrs Freeman lived on Wednesday evening, then seven minutes later to Ms Betteridge's address in Byland Close.
Ms Freeman's children Sarah Helm, 28, James Helm, 27, Kimberley Helm, 25 and Lauren Freeman, 18, previously said in a statement: "We shouldn't have to be writing a tribute to our mother who was taken from us so early. She should still be here to watch her four kids and grandkids grow."
In tribute to Ms Betteridge, Theresa Largan, 51, said: "Jodie lived for her kids. I don't think I ever saw her on her own, she always had the tribe with her."

The former party leader's victory came as the SNP won all six seats in the north east of Scotland.
Callum McCaig won Aberdeen South from Labour, and Kirsty Blackman did likewise in Aberdeen North.
Stuart Donaldson won West Aberdeenshire and Kincardine, Angus Robertson held Moray, and Eilidh Whiteford was re-elected in Banff and Buchan.
However, Alistair Carmichael retained Orkney and Shetland for the Liberal Democrats.
Mr Salmond, speaking after defeating the Liberal Democrats in Gordon, said: "The Scottish lion has roared this morning across the country.
"There is a swing under way in Scotland the like of which has not been seen in recorded politics.
"I look forward to representing every constituent, regardless of their political views."
Mr Salmond claimed a 47.7% share of the vote, over Christine Jardine on 32.7%, as the SNP saw a 25.5% increase.
Mr McCaig's win, with a 29.8% increase, saw Anne Begg lose her seat. He said he was "honoured and thrilled".
Ms Blackman's win was on the back of a 34.2% increase to defeat Richard Baker.
Mr Donaldson's West Aberdeenshire and Kincardine victory came after a 25.9% share increase. Lib Dem Sir Robert Smith, who lost the seat, was pushed into third behind Conservative Alexander Burnett after a 17% fall.
Mr Robertson increased his majority for a 49.5% share, as did Ms Whiteford, with a 19% vote increase and a 60.25% share.
Mr Carmichael's victory came after a 20.6% fall in his share of the vote.
He thanked the people of Orkney and Shetland for giving him the "tremendous privilege" of serving them again.
Peterborough United have signed striker Junior Morias from National League South side St Albans for an undisclosed fee on a two-and-a-half year deal.
[NEXT_CONCEPT]
Cardiff's local TV channel, Made In Cardiff, has announced that it will begin broadcasting programmes on 15 October at 20:00.
[NEXT_CONCEPT]
A man has appeared in court accused of murdering two women within minutes of each other in separate attacks.
[NEXT_CONCEPT]
Alex Salmond said the Scottish lion had "roared", after he won the Gordon seat for the SNP in the general election.