The answer is a resounding yes. Pakistan began sponsoring anti-India terrorists around the late 1980's and early 1990's (to ferment unrest in Kashmir because it lost conventional wars), and several former Pakistani Prime Ministers and Presidents have publicly accepted this fact. Of course, they were usually referred to as "freedom fighters" etc.
See the section called "Admission of state sponsored terrorism by Pakistani authorities" at this link for further references. Some quotes from referenced links:
SPIEGEL Interview with Pervez Musharraf
SPIEGEL: Why did you form militant
underground groups to fight India in
Kashmir?
Musharraf: They were indeed formed.
The government turned a blind eye
because they wanted India to discuss
Kashmir.
SPIEGEL: It was the Pakistani security
forces that trained them.
Musharraf: The West was ignoring the
resolution of the Kashmir issue, which
is the core issue of Pakistan. We
expected the West -- especially the
United States and important countries
like Germany -- to resolve the Kashmir
issue. Has Germany done that?
SPIEGEL: Does that give Pakistan the
right to train underground fighters?
Musharraf: Yes, it is the right of any
country to promote its own interests
when India is not prepared to discuss
Kashmir at the United Nations and is
not prepared to resolve the dispute in
a peaceful manner.
Also, from the same interview in 2010, allegations of continued training of terrorists in Pakistan.
SPIEGEL: A German member of the
militant Islamic Movement of
Uzbekistan, 36-year-old Ahmad Sidiqi,
who has been held by US forces in
Afghanistan since July, allegedly told
his American interrogators that he was
trained in Pakistan and confessed
there were plans to attack Europe.
Why, nine years after 9/11, does
Pakistan remain a breeding ground for
international terrorism?
Musharraf: We poisoned Pakistani civil
society for 10 years when we fought
the Soviets in Afghanistan in the
1980s. It was jihad and we brought in
militants from all over the world,
with the West and Pakistan together in
the lead role. After the withdrawal of
the Soviet troops, the West left
Pakistan with 25,000 mujahedeen and
al-Qaida fighters, without any plan
for rehabilitation or resettlement.
While you were mostly concerned with
the reunification of Germany, we had
to cope with this. Now you expect
Pakistan to pull out a magic wand and
make all of this suddenly disappear?
That is not doable -- this will take
time.
From The Hindu, July 2009
Islamabad (PTI): For the first time,
Pakistan President Asif Ali Zardari
admitted that militants and extremists
were "created and nurtured" in the
country as a policy to achieve some
short-term tactical objectives.
Also, some confessions from Guanatanamo Bay detainees regarding ISI (Pakistan's primary intelligence and covert organization) support provided to terrorists, according to Wikileaks. From the introduction:
The ISI facilitated militants to cross
the border to carry out strikes on
Indian targets chosen by the Pakistan
Army, several detainees at the
Guantanamo Bay facility told US
interrogators, according to a fresh
set of American diplomatic cables
released by WikiLeaks.
The Pakistani army was also implicated (though not conclusively proved) to be involved in the Mumbai 2008 terrorist attacks, where all the participating terrorists had been given "commando training".
"Kasab in his confession has said one
Major General was present during their
training and supervised the firing
practice. The name of this Major
General was deliberately not revealed
to the attackers as he occupies a
senior position in the army," Nikam
said.
The support continues even now, but due to changing factors, the terrorists they support have now come into the global limelight(due to links with Al-Qaeda of course).
Since terrorists receive support from the army, democratically-elected or coup-instated government heads and intelligence agencies, it would be fair to say that Pakistan is a state sponsoring terrorism.